December 2008 - Boost-users

[Spirit] Building an expression parser with boost.spirit
by Max 24 Dec '08

24 Dec '08

Thank you! It's really a vault full of spirit examples from beginning tutorials to full-fledged applications! Best regards Max ----- Original Message ----- From: Joel de Guzman To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit Date: 2008-12-24 11:07:20 Max wrote: > Thank you Hartmut. > > I've found some simple examples using Google and an > expression parser, exactly as what I described, which is > built on boost.spirit: > > http://idlebox.net/2007/stx-exparser/#subsec_grammar Also, see http://spirit.sourceforge.net/repository/applications/show_contents.php Spirit2 has extensive calculator examples from the simplest expression evaluator progressing incrementally to a full C-like compiler. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit
by Max 24 Dec '08

24 Dec '08

Thank you Hartmut. I've found some simple examples using Google and an expression parser, exactly as what I described, which is built on boost.spirit: http://idlebox.net/2007/stx-exparser/#subsec_grammar Best regards Max ----- Original Message ----- From: Hartmut Kaiser To: Subject: Re: [Boost-users] [Spirit] Building an expression parser with boost.spirit or any other Date: 2008-12-23 22:41:43 > There are several parsing tool libs in boost, say spirit and wave, > pheonix, etc. > But I am just not quite clear of the relation between each of them. > I've skimmed through some of the documentation some time ago, but it > seems to be too tough to me till now. > > My question is, giving the huge power of these libs, is it simple to > construct an traditional expression parser which accepts formulea like: > > 1+2/3 > sin(0.34)/power(tan(.4),3) > and so on > > Or, preferably, is there already a sample program like this anywhere? I'd say, go with Spirit. Examples are for instance in the Spirit distribution ($BOOST_ROOT/libs/spirit/examples) and here: http://spirit.sourceforge.net/repository/applications/show_contents.php. HTH Regards Hartmut ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Accumulators: Using data vector from Interprocess
by dhruva 24 Dec '08

24 Dec '08

Hi, I have large data to be processed hence planning to use memory mapped file backed vector from boost::interprocess. Could I use this vector directly in accumulators and perform computations on data in the boost::interprocess container without having to copy it all into the contain in accumulator_set? Also, is there a way to remove an entry once I add it to an accumulator_set? I want to emulate a sliding window calculation. Ex: If my window size is 100, when I add the 101st entry, I want to remove the 1st entry so that the size is always 100. -dhruva -- Contents reflect my personal views only!

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Re: [Boost-users] [STL] Is there a std::abs<>() function?
by Max 24 Dec '08

24 Dec '08

Hello Anteru, Yes, there exist several overloads of abs() functions or similar but some of them with different name, say fabs, fabsf, etc. This make it impossible to use it in generic code. More specifically, I've ever written this code cout << std::abs<int>(-1) << endl; but, to my very surprise, I get 0! I have #include <cmath> #include <cstdlib> I'm using VS2003SP1 under WinXP_SP1 Thanks B/Rgds Max ----- Original Message ----- From: Anteru To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? Date: 2008-12-23 19:00:56 Max schrieb: > Hello, > > It's strange to me that there seems not to be a std::abs<>() function > in STL, with it I can write code like this: > > double d = std::abs(-1.0); > int i = std::abs(-1); > > Does anybody else have the same feeling? #include double d = std::abs (-1.0); cmath pulls the standard math functions into the std namespace, and adds a few overloads. See for example: http://www.dinkumware.com/manuals/?manual=compleat&page=math.html#abs Cheers, Anteru ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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[Statechart] Order of Trigger/Event/Guard at state transition
by Franz Alt 23 Dec '08

23 Dec '08

Hi all, I've tried to use the Statechart library for modelling a simple state machine. I've created three states and three transitions between them and added some debug outputs. When I've looked to the debug outputs I've wondered a little bit. I've thought that the processing of events are in the order 1) exit actions of source state 2) transition actions and 3) entry actions of target state. When I look at my result I see the order 1) transition action 2) exit action of source state and 3) entry action of target state. Does anybody know what I'm doing wrong here? Best regards, Franz #include <iostream> #include "FSMSimple.h" using namespace std; int main(int argc, char * argv[]) { // Instanciate the FSM ... FSMSimple sm; // ... and start it sm.initiate(); // Process some events ... cout << "trigger event 'Event1'" << endl; sm.process_event(Event1()); cout << "trigger event 'Event2'" << endl; sm.process_event(Event2()); return 0; } #include "FSMSimple.h" #include <iostream> using namespace std; // The FSM void FSMSimple::action1(const Event1 & /*e*/) { cout << "process action 'action1'" << endl; } void FSMSimple::action2(const Event2 & /*e*/) { cout << "process action 'action2'" << endl; } void FSMSimple::action3(const Event2 & /*e*/) { cout << "process action 'action3'" << endl; } bool FSMSimple::guard1() { cout << "process guard 'guard1'" << endl; return true; } // FSM state 'StateA' StateA::StateA() { cout << "enter state 'StateA'" << endl; } StateA::~StateA() { cout << "leave state 'StateA'" << endl; } // FSM state 'StateB' StateB::StateB() { cout << "enter state 'StateB'" << endl; } StateB::~StateB() { cout << "leave state 'StateB'" << endl; } sc::result StateB::react(const Event2 & e) { if (context<FSMSimple>().guard1()) { context<FSMSimple>().action3(e); return transit<StateC>(); } else { context<FSMSimple>().action2(e); return transit<StateA>(); } } // FSM state 'StateC' StateC::StateC() { cout << "enter state 'StateC'" << endl; } StateC::~StateC() { cout << "leave state 'StateC'" << endl; } #ifndef FSMSIMPLE_H #define FSMSIMPLE_H #include <iostream> #include <boost/mpl/list.hpp> #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/custom_reaction.hpp> #include <boost/statechart/transition.hpp> namespace mpl = boost::mpl; namespace sc = boost::statechart; // FSM events struct Event1 : sc::event<Event1> { Event1() { std::cout << "process event 'Event1'" << std::endl; } }; struct Event2 : sc::event<Event2> { Event2() { std::cout << "process event 'Event2'" << std::endl; } }; // FSM initial state struct StateA; // The FSM struct FSMSimple : sc::state_machine<FSMSimple, StateA> { void action1(const Event1 & e); void action2(const Event2 & e); void action3(const Event2 & e); bool guard1(); }; // FSM states (forward declarations) struct StateA; struct StateB; struct StateC; // FSM states struct StateA : sc::simple_state<StateA, FSMSimple> { typedef mpl::list< sc::transition<Event1, StateB, FSMSimple, &FSMSimple::action1> > reactions; StateA(); ~StateA(); }; struct StateB : sc::simple_state<StateB, FSMSimple> { typedef mpl::list< sc::custom_reaction<Event2> > reactions; StateB(); ~StateB(); sc::result react(const Event2 & e); }; struct StateC : sc::simple_state<StateC, FSMSimple> { typedef mpl::list< > reactions; StateC(); ~StateC(); }; #endif // FSMSIMPLE_H enter state 'StateA' trigger event 'Event1' process event 'Event1' leave state 'StateA' process action 'action1' enter state 'StateB' trigger event 'Event2' process event 'Event2' process guard 'guard1' process action 'action3' leave state 'StateB' enter state 'StateC' leave state 'StateC'

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[Units] How to use units from different systems
by Juan José Icaza 23 Dec '08

23 Dec '08

I am trying to use the boost::units library for the first time. I'm able to use the SI system. However, I would like to use units from different systems. Particularly, I would like to be able to write: quantity<si::length> L = 3.0 * us::inch + 0.50 * si::meter; The library comes with a us::inch_base_unit. But I don't know how to create a us::inch unit. Any help is appreciated. Juan José

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Graph-Based Threaded Algorithms
by James C. Sutherland 23 Dec '08

23 Dec '08

I am looking for some guidance from some of the graph and thread experts out there. I have a graph that I want to execute a breadth-first search (BFS) on. When each node is visited, it spawns a thread to execute some work. I must not execute a child node before the parent execution is completed, but I also want to maximize concurrency. In other words, I don't want to "serialize" the BFS to force proper execution ordering. Are there any ideas of how to accomplish this efficiently? James --- James C. Sutherland Assistant Professor, Chemical Engineering The University of Utah 50 S. Central Campus Dr, 3290 MEB Salt Lake City, UT 84112-9203 (801) 585-1246 http://www.che.utah.edu/~sutherland

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Determine base class member function pointer for member function pointer of derived class.
by Siegfried Kettlitz 23 Dec '08

23 Dec '08

Hello, is there an automatic way to determine the base class member function pointer &base::fn from the derived member function pointer &derived::fn? Or do you know that there is no way to do this with current c++? It should work like this: class base { public: virtual void fn( void ); }; class derived : public base { public: void fn( void ); } main() { base_pointer = get_base_pointer( &derived::fn ); } Thanks, Siegfried

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Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 23 Dec '08

23 Dec '08

Hello Scott I'm not sure what you mean by ADL? Thanks for reply. Best regards Max ----- Original Message ----- From: Scott McMurray To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-23 12:42:48 On Mon, Dec 22, 2008 at 21:06, Max wrote: > > What I need is a template version of abs, not the > int abs(int) function, to make use of it genericly. > Do you really need a template of it? I can't see why using ADL wouldn't be enough (with a using declaration for std::abs, to catch the overloads for scalars from and ). ~ Scott ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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Re: [Boost-users] [STL] Is there a std::abs<>() function? (Max)
by Max 23 Dec '08

23 Dec '08

hello Philip, Thanks for your reply. What I need is a template version of abs, not the int abs(int) function, to make use of it genericly. B/Rgds Max ----- Original Message ----- From: Philip Ogunbona To: boost-users(a)lists.boost.org Subject: [Boost-users] [STL] Is there a std::abs<>() function? (Max) Date: 2008-12-22 23:45:52 Max, Using STL does not prevent access to abs(), fabs() and labs(). You just need to #include . Is that what you want? Philip ------------------------------------------------------------------- 新浪空间——与朋友开心分享网络新生活！(http://space.sina.com.cn/ )

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